<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var str = "hello";
        var reg = str.slice(2,4)
        console.log(reg);//ll
        var a = reg.split("")
        console.log(a);
        console.log(a.join("-"));
    </script>
</body>
</html>